<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>Document</title>
	<script type="text/javascript" src="js/jquery-1.12.4.min.js"></script>
	<style type="text/css">

		*{
			margin:0;
			padding:0;
		}
		
		.list_con{
			width:600px;
			margin:50px auto 0;
		}

		.inputtxt{
			width:550px;
			height:30px;
			border:1px solid #ccc;
			text-indent:10px;
		}

		.inputbtn{
			width:40px;
			height:32px;
			border:1px solid #ccc;
		}

		.list{
			list-style:none;
			margin-top:20px; 
		}

		.list li{
			height:40px;
			line-height:40px;
			border-bottom:1px solid #ccc;
		}

		.list li span{
			float:left;
		}

		.list li a{
			float:right;
			text-decoration:none;
			margin:0 10px;
		}

	</style>
	<script type="text/javascript">
		
		$(function(){

			var $inputtxt = $('.inputtxt');
			var $btn = $('#btn');
			var $ul = $('.list');

			$btn.click(function(){

				var $val = $inputtxt.val();

				if($val==''){
					alert('请输入内容');
					return;
				}

				var $li = $('<li><span>'+$val+'</span><a href="javascript:;" class="up">↑</a><a href="javascript:;" class="down">↓</a><a href="javascript:;" class="del">删除</a></li>');

				$ul.append($li);
				$inputtxt.val('');

			});


				$ul.delegate('a', 'click', function(){
					
					$handler = $(this).prop('class');

					if($handler=='del'){
						$(this).parent().remove();
					}

					if($handler=='up'){
						if($(this).parent().prev().length==0){
							alert('到顶了');
							return;
						}

						$(this).parent().insertBefore($(this).parent().prev());
					}

					if($handler=='down'){
						$(this).parent().insertAfter($(this).parent().next());

						if($(this).parent().next().length==0){
							alert('到底了');
							return;
						}						
					}					
				});
		})
	</script>
</head>
<body>
	<div class="list_con">
		<h2>To do list</h2>
		<input type="text" id="txt1" class="inputtxt">
		<input type="button" name="" id="btn" value="增加" class="inputbtn">
		<ul id="list" class="list">
			<li>
				<span>学习html</span>
				<a href="javascript:;" class="up">↑</a> 
				<a href="javascript:;" class="down">↓</a>
				<a href="javascript:;" class="del">删除</a>
			</li>
			<li>
				<span>学习javascript</span>
				<a href="javascript:;" class="up">↑</a>
				<a href="javascript:;" class="down">↓</a>
				<a href="javascript:;" class="del">删除</a>
			</li>
			<li>
				<span>学习css</span>
				<a href="javascript:;" class="up">↑</a>
				<a href="javascript:;" class="down">↓</a>
				<a href="javascript:;" class="del">删除</a>
			</li>
		</ul>
	</div>
</body>
</html>